The present invention relates to power stackers employed to collect and stack envelopes or the like.
U.S. Pat. No. 5,137,415 describes a power stacker having a base section both a deck and a laterally positioned registration wall. One end of the power stacker is aligned to the ejection end of a postage meter mailing machine. The other end of the power stacker has a displaceable end wall. The displaceable end wall of the power stacker is vertically reclined and utilizes support rods slidably mounted in the base, one end of the displaceable wall being mounted to the displaceable end wall. Endless belts are mounted within the base such that a portion is exposed along slots in the deck. The belts are driven by a drive train such that received envelopes are transported along the deck in a shingled manner to a plurality of threaded hubs. It is the function of the threaded hubs to engage the trailing end of the respective envelopes and cause the respective envelopes to assume a reclined vertical orientation biased by the displaceable end wall. The collection of envelopes causes the displaceable end wall to displace laterally under the influence of the collected envelopes. The power stacker further includes pivotally mounted on the registration wall a power stack wheel assembly for providing a biasing force to the stream of shingled envelopes being transported by the belts. A detailed description of a suitable power stack wheel assembly is presented in U.S. Pat. No. 5,186,452.
It is the intended purpose of the power stacker to consistently stack envelopes of varying weight, thickness and paper roughness. Envelopes are to be received by the power stacker in a seriatim manner. The envelopes are first collected on the deck of the power stacker in a shingled manner and then transported to the stack wall for vertically directed collection. Empirical testing of the described power stacker, in combination with a particularly suited postage meter mailing machine, has demonstrated certain combination of envelopes of varying weight, thickness and paper roughness under certain operating perimeter are not properly received by the power stacker to produce a suitable shingling of the mail stream. As a result, under those conditions the mail stream is improperly transported along the deck in a misaligned manner for proper stacking against the displaceable stack wall. It has been postulated that the projection angle of the envelope should be maintained within a specified range which is a function of envelope size, thickness and weight.